rar增量求助！

如何用winrar做增量？
将 D:\data 做增量到 D:\backup
\data里有N个文件夹例如 a1 b1 c1 d1
打包到 D:\backup\a1.rar
D:\backup\b1.rar
D:\backup\c1.rar
.....请问这样哪里错了呢？？？FOR /F %%i IN ('dir /a:d /b "D:\data"') DO (
"C:\Program Files\WinRAR\rar.exe" a -IBCK -agYYYYMMDD -tn1D -r "D:\backup\add\%%i" "D:\data\%%i"
)